Recovery of pentoses and hexosans from wood liquors



hum y 9 is I aacovanr or rau'rosas AND mosms M woon uouoas Horace E. Hall, Lyle, Term. and Lester L. Cole- I man, Wilmington, Del,

Corporation, Laurel, Mira, a corporation oi Delaware ellllllorl' to Masonite No Drawing. Application March 31. 1944."

Serial m. 529,:

This invention relates to enzymatic hydrolysis of non-cellulosic carbohydrate anhydrides. or sugar precursors, i. e.. materials from which sugars may be formed, and more particularly to the selective enzymatic hydrolysis of precursors of pentose sugars.

It further relates to a process including the utilization of selective enzymatic hydrolysis upon solutions containing mixtures of sugar precursors, whereby the precursors of pentose sugars are hydrolyzed to pentose and the remaining sugar precursgrs are unailected and can be separately recovered.

The practice of the process will be described upon wood liquors derived from wood or woody iignovcellulose materials which may be obtained, as by expression or washing, from fiber produced by subjecting wood chips to the hydrolyzlng action high pressure steam in a gun, such as described in U. S. Patent 1,824,221 to Mason, followed by explosive discharge from the gun. Such a liquor is described'in U. 8. Patent No. 2,22%135 to Boehm.

6 Claim!- (Cl. -11) sugars. etc. before the pentose sugars and/or The wood liquor obtained as described contains materials produced from hemicelluloses by the high-pressure steam treatment and which are soluble or dispersible in water. From these materials hexose and pentose sugars may be formed, and while such precursors of hexose and pentose may be in part polyuronides as well as polysans,

they are herein referred to for convenience as hexosans and pentosans. The liquor also contains soluble or dispersed tars, some free sugars, acetic acid. formic acid, soluble or dispersed lignin or lignln-degradation products, astringents. and various other materials.

One modeoi utilizing only the pentose precursor material contained in such wood liquors is described and claimed in the application for U. 8. patent of R. M.-Boehm, Ser. No. 352,399, new Patent 2,369,655. This consists in subjecting the liquor, preferably in concentrated term. to severe hydrolysis in the presence of a mineral acid, carried to such extent that a high yield of iuriural and the like products are obtained. Such relatively harsh hydrolysis treatment degrades the hexcse precursors or hexoses. as by caramelization, tar formation and the like, to the extent of making them'unfit for subsequent fermentation or like treatment.

pentose precursors are subjected to such severe mineral acid hydrolysis treatment.

One object of the invention is to provide a process for eiiecting a selective enzymatic hydrolysis of pentosan material to pentose sugars in a mixture containing pentosans and hexosans, thereby permitting the hexosans to be removed.

A further object is to provide a process whereby both the hexosan content and pentosan content of a solution containing hexosans and pento sans can be utilized by eiiecting an enzymatic hydrolysis of the pentosans and thereby converting the solution to a solution containing mixtures of pentoses and substantially unchanged hexosans, and the hexosans can be removed from the latter solution.

In setting forth the practice of the invention on the wood liquor described above, two embodimerits will be presented for purposes of illustration. In one, such liquor is used without previous purification treatment. In the other, liquor is used from which most or all of the constituents other than pentosans and hexosans have been removed.

When the liquor'to be treated according to the process of the present invention consists of a mixture of hexosan and pentosan material, along with other materialssuch as tars, organic acids. astringents, etc., as in the case of wood liquors above referred to. it may be subjected to enzymatic hydrolysis without preliminary treatment to-eliminate the tars, etc. The enzyme material which has been found best adapted for this purpose is that resulting from the action of the mold Aspergillus niger. Such material may be supplied as by adding bran containing same to the solution. The enzymatic hydrolysis treatment is carried out at suitably low temperatures in the range of about -60 C., which has been found best adapted to secure high yields of pentose. The preparation of the enzyme and bydrolysis treatment therewith will be further described below.

.Wlth use of Aspergillus niger enzymes as the hydrolyzing agent, a very effective conversion of pentosan material to pentose can be obtained.

. 3 This may be instanced by hydrolysis eifects obtained with two batches of liquor which had been 1 produced as above described from pine wood and sum wood respectively. The solid content of such liquors was approximately 4 ports in 100. Upon hydrolyzing the liquor from pine wood with the Aspergillus nicer enzyme, 75% of the pentosans were hydrolysed, with no evidence of hydrolysis of the hexosans. In the case of gum wood 80% oi the pentosans were: hydrolyzed.

After the hydrolysis treatment'lias been com pleted, the liquor is a solution in water of pentoses and hexosans, and containing extraneous= materials, as tars and the like. After removal of the bran, as by filtration, the hexosanslmay ill be separated from the pentoses by addition, to the solution of an oxygenated water-miscibleorganic liquid. as for example acetone, a mixture of acetone and lsopropyl ether, dioxane. or the lower aliphatic alcohols. as methanol or ethme]. As a result of this treatment. the hemsans are apparently dehydrated and are precipitated, and they can be filtered out while the pentoses remain in solution. The precipitated hexesan material may be washed with acetone or the like solvent to remove any tars, etc which have beencarried down with the hexosan material, and may subsequently be used for anydmired purpose, as for example, fermentation to produce organic acids and solvents.

After recovering the additive precipitating agent materials for re-use, which can be done, for example. by low temperature distillation. the remaining liquor may be used for making inri'ural by hydrolyzing the pentose in presence of mineral acid. Thus destruction of hexosans can be avoided and precursors of both hexose and pentcse may be utilized to advantage;

' -While the organic additive material may satisfactorily be used in amounts ranging from 2 to 7 volumes to one volume of's'olution, best results have been obtained with addition of about 4 volumes of the organic additive or precipitating agent material to one volume of solution. While several organic additive materials give satisfactory results, optimum precipitation has been obtainedwhen usinga mixture of acetone and isopropyl ether wherein the acetone is-present in the amount of about 4 volumes to about-one volume or isopropyl ether, although a range of volume ratios, as for example, 3 to 8 volumes of acetone to one volume of isopropyl ether gives satisfactory results. The quantity of additive precipitating agent material to be used can be containing liquor to precipitation treatment before subjecting it to enzymatic hydrolysis. The precipitation of both hexosans and pentosans can be efiected by addition to the liquor of watermiscible organic materials as above described in connection with precipitation of the hexosans. This treatment will allow recovery oi relatively pure hexosans and pentosans which may be dissolved ln water and subjected to the above described enzymatic hydrolysis-treatment. After the" enzymatic hydrolysis-treatment; "the helmsans can readily be separated from the pentose sugars by the previously described precipitation procedure. and the separated components can be treated as desired.

Another mode of eliminating tars. etc., from the wood liquor is that 0! using such materials as dried blood. cetyl amine, and the like to precipitate these undesirable components.

When this procedure using cetyl amine, dried blood or the like-is followed, the solution which is obtained as a filtrate is ready to be subjected to the hydrolyzation treatment with Asperaillus adder or like enzymes. and such treatment together with the remainder of the process proceeds as previously described. 1 s

With use of Aspergillus niger enzyme-tor eifecting hydrolysis. this enzyme materialis-preferably prepared by moistening wheat bran'and inoculating the mass with a few spores of the mold Asperoillus ntger. Mold taken from moldy bread is suitable. The container is shaken occasionally to prevent limping and uneven growth, and within the hydrolysis treatment. I

in about 48 to 72 hours the growth has proceeded to a point where rapid sporulation is evidenced. At this point maximum amounts of enzyme are available and the moldy bran'is spread to dry at room temperature. Whenthe material has been air-dried,-the bran containing the Aspermllus nicer enzymes is ready for use the degree of'coagulation oi the colloidal matter.-

When the hydrolysis is substantially completed.

re ced y concentratin h liquor. Pr l the liquor becomes clear and the colloidal matter after the ennvmatic hydrolysis, as -for exarnp1e',

concentrating to a solidcontent ranging up to about 50%.

Before adding the water-miscible organic material to be used for precipitation of the hexosan material, it is preferable to adjust the pH of the solution. The best results have been obtained.

"with adjustment of the pH to about M.- How- "ever, a range of pH i'rom about 2 to ii isper- 'missible.

' the percentage being based on weight of solution.

When it is desired to obtain the pentose sugars ina' relatively-pure state, and freefroin the tars and other materials contained in woodliquor.

.it is preierable to subject thesug r-precursorsettles'tc the bottom. The liquor may become dark due to solubles in the bran. but: this is ordinarily not objectionable. 1 i

The above. procedures may be modiiledibut the invention embraces modification coming within the spirit and scope of the claims. The theories, which have. been developed as'a result of observation and are expressed above, are presented here only for purposes of explanation and making-full diisclosureyand not for limitation of; the invent on y 4 The precipitation treatment with acetone. mixtures of acetone and isopropyl ether. and the like materials hereinabove described is not claimed per se herein, being covered by an appllcation'of Horace llall and Robert M. Boehm, Serial No. 629,034. flied March 31, 1944.

We claim:: a 1. Process oftreating acid solutions containing pentosans and hexosans, which comprises inamass oculating the solution with Asperaillus niaer,

allowing fermentation of the solution to go forceliulose material.

3. Process as defined in claim 1, and in which the organic solvent is added in amounts ranging from 2 to 7 volumes to .1 volume of solution.

tone. ethers and lower precipitates the pentosans and hexosans, removing the precipitate fromtheliquor, dissolving the pentosans and hexosans, in water, inoculating 4. Process as definedin claim 1, and in which the fermentation goes forward at a temperature between 50 and 60 C.

5. Process as defined in claim 1, and in which aluminum sulfate is addedto accelerate precipitation of the hexosansL 6. Process of treating wood liquors containing pentosans, hexosans and a variety of impurities such as tars, acids, and lignin to separate the pentosans and hexosans from the impurities and from each other, which comprises incorporating with the wood liquor a, water miscible organic solvent chosen from the group consisting of acethe water solution with 'Asperaillus nicer, allowing fermentation of the solution to go forward which selectively hydrolyzes the pentosans to pentoses and leaves the hexosans substantially unchanged, incorporating with the water solution a water miscible organic solvent chosen from the group consisting of acetone, ethers and lower aliphatic alcohols which precipitates the hexosans while the pentoses remain in solution. and then removing the hexosans from the solution. HORACE E. HALL.

LESTER L. COLEMAN.

nsmasuoascrran v The following references are of record in the I file of this patent:

UNITED STATES PATENTS Number Name Date 1,190,953 Renshaw July 11, 1916 1,391,219 Takamine Sept. 20, 1921 1,851,822 Faerber Mar. 29, 1932 2,031,070 Reich Feb. 25, 1936 2,142,739 Wallace Jan. 3, 1939 2,284,500 Worth May 26, 1942 aliphatic alcohols which i 

